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Re: Plot of (2 x^2 - x^3)^(1/3)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112125] Re: Plot of (2 x^2 - x^3)^(1/3)
  • From: Peter <insomnia.berlin at gmail.com>
  • Date: Tue, 31 Aug 2010 04:27:04 -0400 (EDT)
  • References: <i5aqbk$eru$1@smc.vnet.net>

On 28 Aug., 13:02, Bernard <bernard.vuilleum... at edu.ge.ch> wrote:
> I see in Calcul Diff=E9rentiel et int=E9gral, N. Piskounov, Editions
> MIR, Moscou 1970, on p. 210 the graph of (2 x^2 - x^3)^(1/3) with
> negative values for x > 2, something like :
>
> Plot[Piecewise[{{(2 x^2 - x^3)^(1/3), x <= 2}, {-Re[(2 x^2 -
> x^3)^(1/3)],  x > 2}}], {x, -1, 3}]
>
> When I plot this function with :
>
> Plot[(2 x^2 - x^3)^(1/3) // Re, {x, -1, 3}]
>
> I obtain positives values for x > 3. I don't understand why.
> Thank you very much for your help !

Hi Bernard,

maybe you want

Plot[Root[#^3-(2 x^2-x^3)&,1]//Re,{x,-1,4}]

?

Peter


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